1. Field of the Invention
The present invention relates to a caster for use in a wheelchair, furniture, vehicle, and the like which is almost jam-proof and capable of easily climbing over a gap or obstacle.
2. Description of the Prior Art
A caster for a wheelchair etc. comprising a pair of front and rear wheels and an endless belt wrapped around the wheels and designed to be capable of easily passing over a gap is known (for example, refer to Patent Document 1). A caster designed to climb stairs by tracked wheels is also known (for example, refer to Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Publication No. Hei 8-225001
Patent Document 2: Japanese Unexamined Patent Publication No. 2002-3747 (see FIG. 8)
When a caster with an endless belt climbs over a gap, the endless belt is pushed against the gap and depressed inward (i.e., toward the center of a space surrounded by the endless belt or a wrap-around member in the surface of rotation of the endless belt or the wrap-around member; hereinafter referred to as “inward”). The more the endless belt is depressed, the greater the power needed to pass the gap. Accordingly, in the Patent Document 1, many presser rollers are arranged inside the endless belt to prevent the belt from being depressed. However, arrangements of many rollers make a structure for holding these rollers complicated and the entire device large, increasing the weight, and thereby driving up costs.